This invention relates generally to structural frame assemblies. More particularly, this invention relates to frame assemblies, commonly used in the manufacture of windows and the like, that are formed from interconnected longitudinal elongate frame members.
Windows and doors are the most common light and passage openings applied in the building trade, home construction, or the like. Commonly, the windows and doors include a frame that is constructed to be secured to the building structure and which defines the operation area associated with the openable and closable opening. As is readily understood, windows are commonly provided in a number of configurations, such as, for example, casement windows, picture windows, and/or double hung windows. Such terms are commonly associated with the operation of the sashes or lights of the window relative to the frame. Likewise, doors can be provided in a number of shapes and configured as right or left hand and in or out swings. Regardless of the operation, doors and windows are commonly provided in a number of shapes and sizes to satisfy consumer demands.
Traditionally, opening frames formed of wood would be individualized to satisfy various product offerings. The corner connections associated with most such frame structures require particular attention to avoid failure of the frame assembly due to the possible concentration of forces at the connection between the elongate members of the frame assembly, particularly in view of the ever-increasing design demands being placed on the architectural rather than structural requirements of windows and doors. Design pressure (DP) is one metric of the strength of a window and is measured in pounds per square foot (psf). Measurement techniques for DP are further described in ASTM E1300, titled “Standard Practice for Determining Load Resistance of Glass in Buildings.” Windows must satisfy various requirements associated with their implantation. Accordingly, it is believed room exists for improving the frame corner assembly and/or method for connecting elongated frame members to provide better window opening strength performance.
Another important consideration of window and door construction includes the thermal performance of the entire product which includes the frame. Windows progressed from single pane, storm windows, and double pane windows in an effort to improve the thermal performance of the window. The U-factor is a term that is used in the industry to quantify heat transfer. The units for U-factor are British thermal unit (Btu) per hour per square foot of area per degree Fahrenheit temperature difference. The computer programs Therm 5 and Window 5 are industry-standard computer tools used to simulate heat flow through the edge of the glass and window frame regions as well as through the center of glass. These programs also sum up the respective contribution of each component to determine the U-factor for the overall window assembly. These computer programs were developed by the Lawrence Berkeley National Laboratory and are well accepted for assessing the thermal performance of both a given window and window frame. Based on the parameters associated with currently available window structures, it is believed that room exists from improving the thermal performance of a window assembly by manipulation of the construction of the window frame, a portion of which is the only structure between inside and outside atmospheres.
Accordingly, there is a need for a more robust window or door frame system that can be quickly and conveniently assembled and can preferably be assembled from pre-manufactured parts that can be individualized during assembly. There is also a distinct need for a window or door frame assembly that provides better insulative performance than those currently available.